linux-kernel - Re: [PATCH] PCI/sysfs: Fix read permissions for VPD attributes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <e786be1c-c368-4731-a495-b562c87e9f67@app.fastmail.com>
Date: Thu, 07 Nov 2024 18:15:22 +0200
From: "Leon Romanovsky" <leon@...nel.org>
To: "Bjorn Helgaas" <helgaas@...nel.org>
Cc: "Bjorn Helgaas" <bhelgaas@...gle.com>,
 Krzysztof Wilczyński <kw@...ux.com>,
 linux-pci@...r.kernel.org, "Ariel Almog" <ariela@...dia.com>,
 "Aditya Prabhune" <aprabhune@...dia.com>, "Hannes Reinecke" <hare@...e.de>,
 "Heiner Kallweit" <hkallweit1@...il.com>, "Arun Easi" <aeasi@...vell.com>,
 "Jonathan Chocron" <jonnyc@...zon.com>,
 "Bert Kenward" <bkenward@...arflare.com>,
 "Matt Carlson" <mcarlson@...adcom.com>,
 "Kai-Heng Feng" <kai.heng.feng@...onical.com>,
 "Jean Delvare" <jdelvare@...e.de>,
 "Alex Williamson" <alex.williamson@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI/sysfs: Fix read permissions for VPD attributes



On Thu, Nov 7, 2024, at 16:59, Bjorn Helgaas wrote:
> On Thu, Nov 07, 2024 at 01:31:44PM +0200, Leon Romanovsky wrote:
>> On Tue, Nov 5, 2024, at 18:26, Leon Romanovsky wrote:
>> > On Tue, Nov 05, 2024 at 09:24:55AM -0600, Bjorn Helgaas wrote:
>> >> On Tue, Nov 05, 2024 at 09:51:30AM +0200, Leon Romanovsky wrote:
>> >> > On Mon, Nov 04, 2024 at 06:10:27PM -0600, Bjorn Helgaas wrote:
>> >> > > On Sun, Nov 03, 2024 at 02:33:44PM +0200, Leon Romanovsky wrote:
>> >> > > > On Fri, Nov 01, 2024 at 11:47:37AM -0500, Bjorn Helgaas wrote:
>> >> > > > > On Fri, Nov 01, 2024 at 04:33:00PM +0200, Leon Romanovsky wrote:
>> >> > > > > > On Thu, Oct 31, 2024 at 06:22:52PM -0500, Bjorn Helgaas wrote:
>> >> > > > > > > On Tue, Oct 29, 2024 at 07:04:50PM -0500, Bjorn Helgaas wrote:
>> >> > > > > > > > On Mon, Oct 28, 2024 at 10:05:33AM +0200, Leon Romanovsky wrote:
>> >> > > > > > > > > From: Leon Romanovsky <leonro@...dia.com>
>> >> > > > > > > > > 
>> >> > > > > > > > > The Virtual Product Data (VPD) attribute is not
>> >> > > > > > > > > readable by regular user without root permissions.
>> >> > > > > > > > > Such restriction is not really needed, as data
>> >> > > > > > > > > presented in that VPD is not sensitive at all.
>> >> > > > > > > > > 
>> >> > > > > > > > > This change aligns the permissions of the VPD
>> >> > > > > > > > > attribute to be accessible for read by all users,
>> >> > > > > > > > > while write being restricted to root only.
>> >> > ...
>> >> 
>> >> > > What's the use case?  How does an unprivileged user use the VPD
>> >> > > information?
>> >> > 
>> >> > We have to add new field keyword=value in VA section of VPD, which
>> >> > will indicate very specific sub-model for devices used as a bridge.
>> >> > 
>> >> > > I can certainly imagine using VPD for bug reporting, but that
>> >> > > would typically involve dmesg, dmidecode, lspci -vv, etc, all of
>> >> > > which already require privilege, so it's not clear to me how
>> >> > > public VPD info would help in that scenario.
>> >> > 
>> >> > I'm targeting other scenario - monitoring tool, which doesn't need
>> >> > root permissions for reading data. It needs to distinguish between
>> >> > NIC sub-models.
>> >> 
>> >> Maybe the driver could expose something in sysfs?  Maybe the driver
>> >> needs to know the sub-model as well, and reading VPD once in the
>> >> driver would make subsequent userspace sysfs reads trivial and fast.
>> >
>> > Our PCI driver lays in netdev subsystem and they have long-standing
>> > position do not allow any custom sysfs files. To be fair, we (RDMA)
>> > don't allow custom sysfs files too.
>> >
>> > Driver doesn't need to know this information as it is extra key=value in
>> > existing [VA] field, while driver relies on multiple FW capabilities
>> > to enable/disable functionality.
>> >
>> > Current [VA] line:
>> > "[VA] Vendor specific: 
>> > MLX:MN=MLNX:CSKU=V2:UUID=V3:PCI=V0:MODL=CX713106A"
>> > Future [VA] line:
>> > "[VA] Vendor specific: 
>> > MLX:MN=MLNX:CSKU=V2:UUID=V3:PCI=V0:MODL=CX713106A,SMDL=SOMETHING"
>> >
>> > Also the idea that we will duplicate existing functionality doesn't
>> > sound like a good approach to me, and there is no way that it is
>> > possible to expose as subsystem specific file.
>> >
>> > What about to allow existing VPD sysfs file to be readable for everyone 
>> > for our devices?
>> > And if this allow list grows to much, we will open it for all devices 
>> > in the world?
>> 
>> Bjorn,
>> 
>> I don't see this patch in
>> https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/log/?h=next
>> So what did you decide? How can we enable existing VPD access to
>> regular users?
>
> I think it's too risky to enable VPD to be readable by all users.

So what about to enable it for mlx5 devices?

Thanks

>
> Bjorn